1. Field of the Invention
The present invention relates to a battery pack capable of cooling battery cells housed in a case thereof.
2. Description of Related Art
Japanese Patent Application Laid-open No. 2010-123298 describes a battery pack having a structure in which a case housing battery cells is connected to a fan unit through a duct. In this battery pack, there is formed a circulation of the air which is blown out from the fan unit, distributed to the battery cells to exchange heat with them and then sucked into the fan unit.
However, the battery pack described in the above patent document has a problem in that since the air cooling the battery cells is circulated in a closed space, although noise can be suppressed from leaking to the outside, the cooling performance becomes insufficient when the ambient temperature is high because heat radiation to the outside is suppressed.
There is known a battery pack of the air supply/exhaust type having the structure in which the air taken into a case is supplied to battery cells, and is discharged to the outside after being increased in temperature due to heat exchange with the battery cells. However, the battery pack of this type has a technical challenge in that it is difficult to cool the battery cells evenly because there is difference in air distribution capacity among the battery cells depending on the air flow amount or the flow rate of the air circulating in the case.